Material transport vehicles and systems, such as fork lift trucks, tuggers, and the like, are used in a wide variety of applications. Such vehicles can include manned vehicles and automated guided vehicles (AGVs). Some such vehicles and systems can include sensors and scanners used for navigation and safety.
FIG. 1 is a top view and FIG. 2 is a perspective view of a material transport vehicle 100 that includes a bottom laser range scanner 110 and a laser range scanner 104 mounted near a top of the vehicle, in accordance with the prior art. Both of laser scanners 110 and 104 are used for safety.
A mast 103 can be part of or connected to vehicle 100. A light 102 is mounted on the mast 103 to communicate signals to nearby individuals, such as signals used for warning and safety purposes. The laser scanner 104 is also mounted on mast 103.
Bottom laser scanner 110 is mounted on a front portion of the vehicle 100 at a set height from a ground surface upon which the vehicle travels. The bottom laser scanner 110 projects a laser beam in front of the vehicle 100 to define two zones, a safety zone 112 and a warning zone 114. If the bottom laser scanner detects a body or object (collectively “body”) in the safety zone 112 the scanner can send a signal to a controller (not shown) of the vehicle 110 which in turn communicates to the drive mechanisms (also not shown) of the vehicle 110. In response to receipt of a signal indicating detection of a body in the safety zone 112, the controller can cause the drive mechanisms to halt movement and/or operation of the vehicle. The controller can also cause light 102 to signal the presence of the condition. In this way, bottom laser scanner can be useful for providing safety relative to a body in front of the vehicle 100.
When a body detected in the warning zone 114, the bottom laser scanner 110 can send a signal to the controller. The controller, rather than halting operation, could cause the drive mechanism to slow operation and could cause the light 102 to communicate a warning signal. Such detections could also cause audible alarms to be activated.
Since the bottom laser scanner 110 projects parallel to the ground surface, objects beneath or above the plane are not detected. The use of laser scanner 104 enables the safety zone to be extended to a third dimension, because the laser scanner 104 creates a scanning plane that projects from the laser scanner 104 to about a front edge of the safety zone 112, but also below the plane of the bottom laser scanner 110 to about the ground surface. The scanning plane produced by the laser scanner 104 is referred to as a “light curtain” 116. Like bottom scanner 110, laser scanner 104 also communicates signals to the controller. The controller can exercise an algorithm for causing the appropriate warning signals and drive mechanism control. For example, the controller can determine what to do if the laser scanner 104 detected a body momentarily, but the bottom scanner 110 never detected a body.